Comparative Study of Antioxidant and Physicochemical Properties of Gracilaria fisheri Agar Obtained using Ultrasound-assisted Extraction without and with Enzymatic Treatment

Noorain Nasuha Omar; Nor Hayati Ibrahim; Nizaha Juhaida Mohamad; Nurmahani Mohd Maidin; Herlina Marta; Shamini Nair Achudan

Authors

Noorain Nasuha Omar Faculty of Food Science and Agrotechnology, Universiti Malaysia Terengganu, 21030, Kuala Nerus, Terengganu, Malaysia
Nor Hayati Ibrahim (1) Faculty of Food Science and Agrotechnology, Universiti Malaysia Terengganu, 21030, Kuala Nerus, Terengganu, Malaysia; (2) Functional Food RIG, Food Security in a Changing Climate SIG, Food Security Research Cluster, Universiti Malaysia Terengganu, 21030 Kuala Nerus, Terengganu, Malaysia https://orcid.org/0000-0002-6091-9081
Nizaha Juhaida Mohamad Faculty of Food Science and Agrotechnology, Universiti Malaysia Terengganu, 21030, Kuala Nerus, Terengganu, Malaysia https://orcid.org/0000-0003-4984-2324
Nurmahani Mohd Maidin Faculty of Food Science and Agrotechnology, Universiti Malaysia Terengganu, 21030, Kuala Nerus, Terengganu, Malaysia https://orcid.org/0000-0002-1344-8109
Herlina Marta Department of Food Technology, Faculty of Agro-Industrial Technology, Universitas Padjadjaran, Sumedang 45563, Jawa Barat, Indonesia
Shamini Nair Achudan Farm’s Best Food Industry Sdn. Bhd., Lot 37 & 38, Masjid Tanah Industrial Area, 78300 Masjid Tanah, Melaka, Malaysia

Keywords:

Red Seaweed, Sulfated Agar, Enzymatic Treatment, Green Extraction, Antioxidant, Melting Behaviour

Abstract

Ultrasound-assisted extraction (UAE) is increasingly utilised in agar extraction as an alternative to conventional methods. However, the UAE alone may not be sufficient to maximise the functional quality of agar. In this study, we compared the antioxidant and physicochemical properties of Gracilaria fisheri agar (AGF) extracted using UAE, without and with enzymatic treatment (0.006% Viscozyme^® L), referred to as UAEE. The extraction was done using a solid-to-water ratio of 1:98, an ultrasonic power of 506 W, and a temperature of 60 ⁰C. The AGF from UAEE exhibited significantly (p < 0.05) lower IC₅₀ value (0.13 mg/mL) than that from UAE (0.49 mg/mL), indicating a reduced amount of sample necessary to neutralise half of the 2,2-diphenyl-1-picrylhydrazyl (DPPH) free radicals. Additionally, UAEE provided AGF with a significantly (p < 0.05) higher ascorbic acid equivalent antioxidant capacities (AAEC) of 11125.78 mg AA/100 g, compared to 2829.82 mg AA/100g for UAE. The enhanced antioxidant activity of AGF from UAEE may be attributed to its higher contents of total phenolic compounds, total sugars, and sulfate. Despite its higher sulfate content, it exhibited significantly (p < 0.05) higher melting properties, signifying its superior gelling properties over AGF from the UAE. However, it showed significantly (p < 0.05) lower ferric reducing antioxidant power, likely due to its lower galacturonic acid content relative to AGF from UAE. Overall, combining the UAE with enzymatic treatment resulted in a significantly higher AGF functional quality, offering a promising approach for the efficient and sustainable AGF extraction.

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